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B Madjarov; A New Secure Image File Format for Ophthalmic Digital Images . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2555.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To develop and test a new secure ophthalmic digital image format. Currently there is no common image file format for color or grayscale ophthalmic digital images. Although file formats such as TIFF, JPEG, BMP and others have been randomly used they carry limitations of file size, image quality, flexibility and security. Methods: The design of the new image file format RIF (Reading Center Image Format) is based on common imaging file standards and high level programming language. The format created is vendor independent royalty-free and patent-free. Desired capabilities incorporated were: lossless compression, up to 48 bits per pixel, metadata, color and tonal correction profiles embedding. To test its quality, accuracy and validity a graphical user interface was developed with conversion capabilities between known image formats and RIF. One hundred and seventy digital fundus images with a file size ranging 300KB-25MB were randomly selected and converted to RIF format. For each image, metadata containing arbitrary patient identification number, name code, visit number and clinical center were entered and saved as a part of the file. All images were saved as RIF and BMP file format. To test the accuracy a pixel map was generated from the RIF data and judged against the pixel map from BMP data. Results: The conversion application tested on Pentium III computer, revealed fast and reliable transfer of image data between the file formats. The transfer rate of 1-25 sec. was a function of the file size. Preservation of metadata was 100 % accurate and reproducible. Compression ratio varied with the image size and bit depth from 1.2-2.5. Image data retaining accuracy tested on the image map in 50 locations did not reveal any data loss, misinterpretation or value deviations. Five popular imaging applications failed to recognize and open the RIF file format, which is an indication of reliable security. Incorporated encryption of non-image data, did not allow direct view of the embedded information. Conclusion: The validation study results demonstrated significant security, flexibility and portability over the conventional formats as required in contemporary ophthalmology. A new advanced image file format for the purposes of ophthalmic digital images and digital photograph reading centers is feasible.
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